Telephone system



Jan. 30, 1934. v H. M. FRIENDLY TELEPHONE SYSTEM Filed Oct. 20, 1922 15 Sheets-Sheet 2 Inverflur Herb er'i-P'l-Fr'iandlg WV Aim H. M. FRIENDLY TELEPHONE SYSTEM Jan. 30, 1934.

Filed Oct. 20, 1922 15 Sheets-Sheet 3 m Nm Inveniur- Herb EPvP'I-Fr'iEndl -95 mm xuE MAM 1 H. M. FRIENDLY 1,945,467

' TELEPHONE SYSTEM Filed Oct: 20, 1922 1s Sheets-Sheet 4 3; Q i5? mu JHI- v 3n 3Q n M 1 J1 J] g I t}, T' r T' Q 21: m HI' [n L M g fifi-lHl-Efi F 3 w W' 'WT E?? F 0 i Inveniur- E [E Herb art-PI-Ffiendlg Jan. 30, 1934. H. M. FRIENDLY 1,945,467

TELEPHONE SYSTEM Filed Oct. 20, 1922 15 Sheets-Sheet 5 Jan. 30, 1934. H. M. FRIENDLY 1,945,467.

TELEPHONE SYSTEM Filed Oct. 20, 1922 15 Sheets-Sheet 6 I 1 q- E T 848 7/4 T 637 6'86 D TB 693 Invenmr- HBIh er'l-Pl-Friendlg UFE Jan. 30, 1934.

H. M. FRIENDLY TELEPHONE SYSTEM Filed Oct Fig-7-.

15 Sheets-Sheet 7 Invsniur- Jan. 30, 1934. H. M. FRIENDLY TELEPHONE SYSTEM Filed Oct. 20. 1922 15 Sheets-Sheet 8 Invenrur- I fierheri-P'I-Friendl Jan. 30, 1934- H. M. FRIENDLY 1,945,467

TELEPHONE SYSTEM Filed Oct. 20, 1922 15 Sheets-Sheet 9 Inveninr- F1 q 5 HerhevrPI-Friendlg JWVW Jan. 30, 1934.

H. M. FRIENDLY TELEPHONE SYSTEM Filed Oct. 20. 1922 15 Sheets-Sheet 10 Fiql'El- Jan. 30, 1934.

H. M. FRIENDLY 1,945,467

TELEPHONE SYSTEM Filed Oct. 20, 1922 15 Sheets-Sheet 11 Flqll- Invenlur Herhefl-P'I-Friendlg H. M. FRIENDLY TELEPHONE SYSTEM Jan. 30, 1934.

Filed Oct. 20, 1922 15 Sheets-Sheet l3 Jam 1934- H. M. FRIENDLY 1,945,467

TELEPHONE SYSTEM Filed Oct. 20, 1922 15 Sheets-Sheet l4 SEYBEJ'IDH 3 4 171 Inverdm Herb ert-P'I-Fr'lendly Jan. 30,- 1934. H. M. FRIENDLY 1,945,467

TELEPHONE SYSTEM Filed 001;. 20, 1922 15 Sheets-Sheet l5 makes firs? Patented Jan. 30, 1934 TELEPHONE SYSTEM Herbert M. Friendly, Portland, Greg; Milton S.

Friendly and Central Republic Trust Company executors of said Herbert M. Friendly, de-

ceased Application October 20,

58 Claims.

The present invention is directed to automatic or machine switching telephone systems; more particularly to systems of the stated general type which contemplate directively progressing a call from a calling station, through the agency of a socalled finger-hole dial calling device, to a called station, wherein mechanism is interposed, the purpose of which is to receive and store the directive impulses sent from the calling station, and re-send. them self-controlled, effective to link the connection from the calling to the called station.

Devices of the present invention are applicable to variations of the stated system, and in fact, to automatic or machine switching systems wherein intermediate storing of directive impulses is not effected, but where the switching mechanism is directly controlled from the calling station.

The present invention contemplates that, depending upon the destination of the call from any calling station, the directive impulses employed will be effective to setting up the connection positively, or setting up the connection through a storing of all or only certain of the directive impulses. the linking mechanism units will be positively operated; in other calls, part of the linking mechanism units will be positively operated, and part indirectly operated through the storage of the impulses received from the calling station and the automatically initiated sending of the stored im ulses, and in other calls the linking mechanism units will be wholly operated indirectly from the stored impulses. In determining the method of completing calls to the various lines when organizing the system, in view of the last foregoing statements, considerations, such as the location of the called line with respect to the calling station, with reference to the office or ten-thousand group wherein the concerned lines terminate or lead from, are taken into account.

Where the calling and the called lines are,

tributary to the same ten-thousand group, for example, the calling party may be given an alternative calling number or digit train which will not only require a fewer number of digit series to be sent, but which will operate to apply the impulses (constituting the digits) directly to the linking mechanism with-out storing. Again, where the called line is located in a different tenthousand group from the one containing the calling line, the latter said method will apply, wherein inter-ofiice trunks will be employed in lieu of local trunks. Moreover, the invention con- That is to say, in certain calls 1922. Serial No. 595,832

templates that the said alternative calling numline leads to a line switch of the well known primary type. The latter switch, in common with other line switches has access to a plu-' rality of secondary line switches of the present invention, there being fewer secondary line switches than primary line switches. The traffic from calling lines is thus converged to a rela--' tively small number of trunks leading to the secondary line switches. The latter stated plan, in general, is not new. However, the secondary line switch of the present invention, is novel, so far as I am aware, in that it has two sets of Wipers, which will be referred to as primary and secondary wiper setsp Each said set of wipers has access to a specific group of trunks leading to corresponding groups of selectors. When the call is initiated, the primary line switch of the calling line will function in the well known manner to seize a trunk leading to the secondary line switch of the present invention. The latter said switch will forthwith seize, if its primary wiper set is resting upon bank contacts corresponding to an idle first selector, or it will hunt and seize an idle first selector. This functioning of the secondary line switch is generally similar to the functioning of the primary line switch, or of secondary line switches which are well known.

The trunks leading to the first selectors accessible to the primary wiper sets of the secondary line switches are also selectively accessible to finder switches, each finder switch corresponding to a companion, interlinked mechanism for receiving, storing and re-sending directive impulses in series constituting digits of called numbers, having in mind that the re-sent impulses may be interpreted from received series diiiering as to number of impulses in each series, and also differing as to the number of series re-sent with respect to the number of series received from the calling station. When a trunk is seized by a secondary line switch, a relay is operated which causes the first available finder switch to forthwith hunt for and seize the concerned trunk, in a manner generally similar to the operation of finder switches in well known systems wherein finder switches seize calling subscriber lines responsive to a line relay thereof actuating. A. tone (which will be termed a dialing tone), is applied audible to the calling party, when the finder switch has seized the trunk, providing the'compani on equipments are then ready to receive directive impulses which constitute the listed, or the referred-to alternative calling number corresponding to the called line; the latter in view of what switching center the calling line leads into, as will appear, presently.

Coincident with setting up a condition in the storing mechanism companion to the finder switch, responsive to the sending c; the first digit series, the first selector will also operate responsive to the said first digit series whereby its wipers will be stepped up into alignment with the level indexed by the said first digit series sent. If the said rst digit series sent, and which is that of the nominal first'dig'it of the called number or its prefix, is the actual first digit of the effective calling number, the selector will rotate-in at the level attained and hunt for the first idle trunk leading to the successive linking en digit series, or it may be destined to a called line requiring the sending of a train of but five digit series. In the latter case, as will appear presently, the called line may be reached by the calling party efiectuating a train of seven digit series, alternatively, or in other words, sending two distinct digit trains irom'a specific calling line may, for example, be effective to setting up a condition in the storing 'mechanism specific to each digit train sent, but resultant to progress the call to the same called line. Thus, two distinctively different set-up conditions in the storing mechanism may actually constitute sim-' ilar stored conditions. 7

An object of the said alternative calling numbers referring to the same called line from a specific calling station, and also other certain stations of the system, possibly, is to enable five pulls or the finger-hole calling device dial to effectuate a complete connection, in lieu of requiring. seven, where the nominal capacity and organization of the exchange system contemplates seven numerical orders of digits. Where seven numerical orders are employed, the first three thereof may refer to thefirst three letters of exchange office name prefixes. These letters correspond to and are the equivalent of digits, since letters and digits will appear as separate designations of the same finger-hole on the dial calling device, used by general subscribers, and on keys of pro-setting deioes, where switchboard operators are concerned as the calling party. The letters are employed for psychological reasons, since a number made up of seven digits would be diiiicult to retain in the mind, and would therefore lead to annoyance due to transposing digits. Finger-hole calling devices having auxiliary letter designations to the numerical designations or" the finger-holes have been used heretofore and are well known. Howdicat'ed name, the corresponding finger-hole may be pulled, followed by the last four digits of the wanted line number. The latter will mean that five pulls of the dial will transmit the complete call, though the nominal organization of the system contemplates seven pulls of the dial, and that th latter number may be alternatively employed in the latter exampled call, by pulling the With regard to the name designations on the dial, it will appear, presently, that the dials of the different ten-thousand groups may have different names at the same numerical position. Moreover, this difference may refer to divisions of the same ten-thousand group. Thus, a certain prefix name, such as Main, for example, may be placed radial with the 2 hole of the dial with relation to a certain ten-thousand group of subscribers telephones, while with relation to another said group, the prefix name Central, for example,may be placed radial with the 2 hole. The pulling of 2 in one case will trunk the initiated call to the Main ten-thousand district, and to the Central ten-thousand district in the other. The last four digits of the listed number will be sent to complete its transmission bearing in mind that the 2 sent may, in each said instance, cause the storing mechanism to interpretthe said 2 into one or more predetermined digits, and transmit them, or the said 2 maybe directly effective (irrespective of the storing mechanism) to extend the initiated call to the point contemplated, as if the listed first three 'pulls had been sent in lieu thereof. It will appear, presently, that the location of each ofilce district and the trafiic and other factors, will determine by What method an initiated call will be extended responsive to the T calling dial, whether the listed or the alternative calling number (if alternative calling number is provided for), is sent by the calling party.

In a large exchange, such as would require seven-digit numbers, ten-thousand or other linegroup units, will be centered in various parts of the exchange territory, as determined from economic and other well known considerations. Direct and indirect (tandemed) trunk lines will serve 'as links in connections between calling and called lines whichdo not belong to the same said line group. One or more That is to say, if the line'group units are From the last foregoing, will be inaniiest that where 'a call is from one to another line of r the same roup unit, three of the 6. its sent will be idle di its, that should the saidunit be the only one, but four calling digits would be required. The seven digits will usually be required in the listed calling numbers to avoid confusion and th necessity of supplying special telephone d. ,ctories for each ten-thousand group, if the latter were practical. Where a subscriber calls lines of his own group from the listed number of seven digits, it thus means that seven digits must be called in each instance. The latter requires more time and efiort on the part of the subscriber, and a longer equipment holding time is entailed in completely progressing a call than would be the case were a less number of digits necessary on calls within his unit, or on local calls, as it will be termed. The present invention contemplates that where the call is destined to a local line, but five pulls of the calling device dial will be required through the use of the alternative calling number, though seven pulls will ordinarily be required where the call is destined to a remote group. It will appear presently, that calls may be likewise completed to called lines in certain remote units by five pulls of the dial. The latter would be employed where a considerable percentage of calls from a particular district or districts are destined to a certain remote district or districts, having in mind that it is possible to divide ten-thousand groups so that pulling the same nominal hole first will refer to a different district, the holes being designated correspondingly on the dials of the said divisions of a tenthousand group. It is thus manifest that where the subscribers dial has the special designation or designations thereon, the subscriber can progress a call to lines of the corresponding tenthousand group with five pulls of the dial, or he may also do this by pulling the listed number of seven pulls. In this case, the subscriber may pull three times as a prefix, or he may pull one time as an equivalent prefix.

Other objects of the invention, and the invention itself will be understood from the following description, having reference to the accompany-- ing drawings in which:-

Fig. 1 is a diagrammatic circuit layout showing the trunk routes and the various corelated equipment elements.

Fig. 2 is a diagrammatic layout of a portion of the system contemplated in the invention, in view of Fig. 1.

Fig. 3 shows a subscribers telephone leading to a line switch PL3. The said line switch, in common with other line switches of its group, has access to secondary line switch SL8, and other secondary line switches of the group containing switch SL3. The secondary line switch SL3, in common with other secondary line switches of its group, has access to alternative groups of selectors, S4 and S'4 in Fig. 4 being selectors of each of two groups, respectively.

Fig. l shows the said selectors S4 and S4. These selectors each have access to selectors of a successive numerical order as shown in Fig. 1.

Fig. 5 shows the first two of a group of finder switches F5 and F5 having access to selector S4 and other selectors of its group.

Fig. 6 shows a numerical order distributer switch NDS, a numerical order commutator switch N06 and a digit finder switch DFG. The latter said switches are interlinked with and companion to finder switch F5.

Fig. 7 is the first numerical order storing switch A7, arranged to store the first digit sent. It is also arranged to store the second and third digits sent under special conditions.

Fig. 8 is the second numerical order storing switch A8.

Fig. 9 is the third numerical order storing switch A9.

Fig. 10 shows the fourth and fifth numerical order storing switches A10 and A'lO.

Fig. 11 shows the sixth and seventh numerical order storing switches All and All. Switches in Figs. 6 to 11 are companion to finder switch F5.

Fig. 12 is a diagrammatic layout of the system, showing the method of sub-dividing tandeming centers.

Fig. 13 is an elevation of the digit finder switch DFG of the present invention.

Fig. 14 is a plan view of the digit finder switch DF6.

Fig. 15 is a detail of the directive impulse springs of the digit finder switch DF6.

Fig. 16 is a plan view of the clutch and cooperating clutch-claw and the supporting yoke, sectioned on line with the top of the clutch of the digit finder switch DF6.

Fig. 17 is an elevation of the said yoke of switch DF6.

Fig. 18 is the clutch-claw and armature of the yoke.

Fig. 19 is an end elevation of the yoke and clutch-claw (shown in Figs. 17 and 18) assembled.

Fig. 20 shows the preferred means of modifying Fig. 6 to insure that the interval between digit series will be more nearly equal, regardless of the number of impulses in the various series.

Fig. 21 is a diagram showing the way of assembling the circuit drawing figures to display the exampled system, disclosing the present invention.

Fig. 22 shows a modification applied to Figs. 3 and 4.

It will be clear, presently, that where the firstdigits sent from the subscribers calling device is that listed in the general subscriber directory, and that it also indexes the level the first selector will rotate-in at in the progression of the call, the storing mechanism will not re-send this first digit, nor will the first selector automatically restore forthwith. The storing mechanism will receive all digits sent by the calling party under the condition of storing any of the digits, but the second digit will, in this case, be the first one effective to being re-sent to the second selector through the operated first selector by way of progressing the call. If the first digit sent by the calling party is not numerically indicative of the bank level accessible to the first selector which will be concerned in the call, the first selector will forthwith restore, after which it will be forthwith re operated from the storing mechanism, so it will be caused to rotate-in at the proper level. This will be followed by the remainder of the digit train pertinent to the called line, as

interpreted by the storing mechanism from the digits received by it, having in mind that in many instances all digits following the first will correspond numerically with the digits sent from the subscribers station. Where the first digit sent by the calling party is the one which in itself designates the ten-thousand group containing the wanted line, the first selector will rotatein at the numerically corresponding level and progress the call over the first idle trunk to the fourth selector in the latter said group. Succeeding digits sent by the calling party will be directly efiective in progressing the call in the latter said group, the storing device becoming released from the connection and subject to other use incidental to the sending of the said first digit l by way of progressing the call, the finder switch and storing mechanism converted consequent to the primary initiation of the call, will be released from the connection without its effective employment in the linking of the connection.

The releasing of the finder switch and the storing mechanism under the stated condition operates to reduce the number of finder switches and companion storing equipments necessary for a given installation, since the converted latter said equipments will be forthwith availablefor use in a subsequent call, though the former call may not yet be completed to the wanted line. Again, where the call is progressed directly from the calling device at the subscribers station, the time of completing the connection will be coincident with the termination of the last digit of the called number, whereas, where the directive impulses are first stored and then re-sent, a very noticeable delay occurs after the calling party has finished his sending, before the connection becomes established. The latter has the efiect of delaying the calling party and of holding converted storing and linking equipments. In a large exchange system the latter idleness factor may ag gregate a considerable equivalent holding period, and therefore necessitate an appreciable percentage of additional storing and linking equipments to oiTset the said idleness factor.

Where the calling party employs the alternative calling number consisting of five digits, and the first digit is not directly effective, the storing mechanism will interpret the first digit into the digit or digits and thensend them by way of linking the call, having in mind that under the stated condition the first selector will automatically restore consequent to the sending of the rst digit, to be forthwith re-operated from the storing mechanism in accordance with the first digit of the interpreted digit train. In this connection, it will be understood that the first digit (of five) sent by the subscriber, under the condition will either be directly effective in progressing the call, or a plurality of digits will be interpreted from the first digit wherein the first digit re-sent will not be the same as sent by the calling party, but this latter statement does not positively hold. That is to say, it will possibly occur that the first digit will be effective to di rectly progress the call through the first selector (which remains set) and at the same time set up a condition in the storing mechanism whereby one or a plurality of successive digits will be sent through the first selector effective to linking successive switches. In the latter case, the successive digits sent by the calling party, following the first, will be re-sent by the storing mechanism. 1

A modification of the stated arrangement is shown, whereby when the calling party sends the listed seven digits in lieu of the alternative five digits, the storing mechanism will operate to disconnect the secondary line switch primary wipers and connect the secondary wipers thereof, causing the said secondary line switch to then hunt and seize the first idle trunk leading to a fourth selector, the call being thereafter directly V progressed from the calling telephone, the storing mechanism being released from the connection consequent to the sending of the third digit. The latter stated modification will apply where the secondary line switch will re-hunt consequent to the sending of a corresponding digit, where five digits constitute the alternative calling number.

A feature of the storing mechanism of the present invention is that when a digit train is sent from the storing device, the intervals between the digit series thereof will be practically equal, regardless of the number of impulses constituted of each digit series. This condition operates to shorten the period of re-sending by the storing mechanism to the possible minimum. The storing mechanism is released at once upon its sending the last digit series, so that it may be forthwith converted to the uses of another call.

Referring to Fig. 1, the dotted enclosure denotes that the enclosed equipment elements are located in or are subordinately tributary to the same tenthousand group. In the present exampled instance, the storing mechanism is located in enclosure A, though it will be understood that the other groups may be likewise equipped with storing mechanisms. That is, the specific descriptions will be applicable to other groups of the exchange system, possibly modified. Connections linked within the said dotted enclosure will involve so-called local trunks only, while connections extending to remote groups will involve so-called inter-office trunk lines. The latter may comprise a plurality of trunlg line sections interlinked at so-called tandeming centers.

The various equipment elements will be comprehended in view of the following references to the third edition of Automatic Telephone Practice. by Harry E. Hershey. The subscribers telephones or sub-stations are the usual common battery series type including a dial calling device as described on pages 18 to 19; the primary line switch PLS is as described on pages 53 to 55; the finder switches F5 and F5 are of the general type as the finder switch described on pages 56 and 57, though modified to operate in accordance with the present invention; the various selectors are as described on pages 59 to 62, having in mind that the selector S4 is modified to operate in accordance with the present invention; the connectors are as described on pages 36 to as; the secondary line switch SL3 is of the same general type as PL3, though modified to operate in accordance with the present invention; the rotary elements of the impulse storing mechanism, wherein a stepping magnet is employed, are of the general type as PLZ as to 1116-- chanical structure, having in mind that the said elements operate both directively and selectively. The detailed operation of the system will be comprehended in View of the calls which will be exampled. It will be understood, of course, that the descriptions and the illustrations do not purport to be exhaustive; only enough of the systern contemplated in the invention being shown and described as has been thought necessary to a full and complete disclosure of'its operating principles and structure, since each commercial embodiment of the invention will incorporate detailed modifications or amplifications to the system exampled, in order to meet the trafiic and service peculiarities to be satisfied in the community to be served. 1 1

With further reference to l, the indicated selectors have their numerical order designated by an under-scored numeral. The telephones are ndicated by small circles;

primary and secondary, combined) by small quares, and the connectors by the letter C underscored. Where a trunk link a dotted portion, it indicates .;he trunk is an inter-oflice one, perhaps l ading to or from a tandeming center, or a ten-thousand group. The calling telephone JJA the line switches the primary line switch PL3; secondary line switch 8L3; first selector 84, and first selector 8'4 are correspondingly designated specifically.

With reference to Fig. 2, it will be understood that the seven-digit system contemplated, will have a potential capacity of one hundred tenthousand line-groups for each of the ten holes of the dial calling devices employed on the telephones 01' the subscribers, or a total of one thousand ten-thousand line-groups. The latter may be divided into one hundred hundred-thousandline groups, each latter said group being made up of its component ten ten-thousand groups. The large circles designated B, C, D and E each indicate a hundred-thousand group. The small circles within the large circles designate a component ten-thousand group. The squares designated 4, 6, '7 and 8 (all under-scored) each indicate a so-c'alled primary tandeming center. The squares 46, 62, 76 and 84 (all under-scored) each indicate a so-called secondary tandeming center. The squares 2 and 3' (both under-scored) each indicate a tandeming center in a route to a special switchboard LD, which may perhaps be the toll recording switchboard.

It will thus appear, in view of the last foregoing, that if a call is initiated at telephone T3, the first selector 84 will be automatically reached through the primary and secondary line switches. The selector 84 has eleven levels (or more, perhaps), each said level having a group of trunks which may extend to a tanderning center. For example, trunks from the fourth, sixth, seventh and eighth levels lead to the 4, 6, 7 and 8 tandeming centers, respectively. The latter said trunks terminate in second selectors in the latter said tandeming centers. The said second selectors have ten levels (or more, perhaps), each said group having a group of trunks which extend to a secondary tandeming center. For example, trunks from the fourth level of the second selector a in the 8 center lead to a third selector 1) in the 84 secondary tandeming center. The said third selector 2) has ten levels (or more, perhaps) each said level having a group of trunks which lead to so-called incoming fourth selectors c in a ten-thousand group. For example, the fifth level of the said third selector 1) has trunks which lead to the selectors c of the 845 (under-scored) ten-thousand group of the 84 hundred-thousand group B. The said fourth selector c has ten levels, each of which has a group of trunks which lead to so-called local fifth selectors in the 84-5 ten-thousand group.

It is thus clear that the incoming fourth selectors c in the 845 ten-thousand group are reached responsive to three digit series, wherein antecedent first, second and third selectors have correspondingly functioned responsive to a train of successive series. The fourth digit series is effective to the local fourth selector 0, determining the thousands group in the 845 ten-thousands group to which the called line belongs. The fifth digit series will then operate the fifth selector to determine the hundreds group of the selected thousands group to which the called line belongs, terminating the extended connection in a connector accessible to one hundred lines in the selected. hundreds group. The last two of the seven digit series will serve to set the wipers of theconnector on the bank contacts of the wanted line and signal thereon.

In view of the foregoing, it will be clear that sending digits 763 will progress the call to an incoming fourth selector (1 in the 763 ten-thousand group of 'the 76 hundreds thousand group;

C. However, as adverted to, certainten-thousand groups may be reached by five pulls of the and moreover, by including but three selece tors antecedent to the connector, for example, the third level of selector 84 has trunks leading directly to incoming selectors e having access to the trunks common with the fourth selectors a in the 467 ten-thousand group ofthe 46 hundred-thousand group E. Also, the eleventh level of selector 84 leads to selectors inthe 62 secondary tandeming center, from whence trunks are accessible through the fifth and sixth levels to fourth selectors h, and g inthe 625 and 626 ten-thousand groups thereof. The latter implies but six digit series (re-sent, inthe present instance, from seven sent by the calling party) to complete the call from the calling line to the called line. In this instance, the calling and called lines are in the same hundred-thousand group, though it will be manifest that the trunks leading from the eleventh level of selector 84 may extend to incoming selectors in any other secondary tandeming center with reference to any other hundred-thousand group. Similarly, the trunks leading from the third level of selector 84 may extend to any other ten-thousand group of the system other than the 9467 of the 46 hundred-thousand group E. I

The alternative selector 8'4, which it will appear, presently, is attained upon the calling party sending impulses corresponding to digit 2, may be alternatively located in any ten-thousand group of the system other than the 623 tenthousand group containing the calling line, as shown. The levels of the selector 8'4 (reached directly from the secondary line switch 8L3), extend to thousands (fifth) local selectors 1', thus entailing but four pulls of the dial to progress the call from the selector 8'4 to the wanted line. It will be manifest, presently, that a single selector (or a plurality) may be introduced intermediate of the selector 8'4 and the thousands selector i of the ten-thousand group to which the wanted line belongs. Under the latter condition, the completion of the call will involve six (or more) digit series, the said selector (or selectors) introduced intermediate of the selector 8'4 and the thousands selector 2' will be located in a tandeming center, or centers. Where the selector 84 is involved in a call, the storing mechanism, which is then associated with the selector 84 will not be concerned, since it will be vacated with its companion selector 84 upon the digit or digits being sent to cause the secondary line switch 8L3 to seize the selector 8'4.

With further reference 'to Fig. 4, the trunks leading from the bank contacts accessible to the Wipers of the selectors 84 and 8'4 are not shown connected.. In view of the citations, and descriptions to follow, it is deemed that the disclosure with relation to the said trunks will be ample, since the trunks outgoing from the latter .said selectors are indicated in Figs. 1, 2 and 12. It will be understood, in this connection, that the inter-office trunks will have impulse repeaters interposed, as has been a well known practice in systems of the general class, in order to translate from three-wire to two-wire operation, and for other reasons.

Assume that party at telephone T3 removes the receiverby way of initiating a call destined to telephone T, tributary to the same ten-thousand: group, the listed calling number of which is 

